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  • Click High Speed Frequency question

    Hi all,

    I have done a program to show the current speed of a machine on a screen. The problem is I am getting erratic readouts because the pulses from the sensor are not even. It goes like this : pulse on,pulse off, pause off,pulse on,pulse off and so on. Looks like I have two objects that the sensor reads in one turn. I cant remove the object from the sensor because it has another function with another PLC.

    If the machine is at 65 RPMs the read out goes 41-65-41-65.

    Is there a way to get the highest reading or smooth the operation ?. the pulse is not fast.

  • #2
    Not sure what you can do in Click, but you may be able to back into out with a high speed timer. In BRX we recommend using a Timer with an Interval Scale for low frequency inputs, rather than a Counter and Rate Scale.

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    • #3
      If the pulse is not that fast, a counter with a setpoint of 2 may work.
      The counter output would be activated every two pulses.
      This would skip one of the inputs.

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      • #4
        Can you count the pulses over a longer time base?

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        • #5
          The CLICK Freq/RPM calculation does not allow for asymmetrical pulses. But you can measure the two separate intervals and calculate it fairly easily. The Interval Measurement is configured to also run an interrupt program after each sample. Inside the interrupt the two previously measured times are added together and then the RPM is calculated.
          Attached Files

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          • #6
            Thank you all, I tried the timer for the pulses and it works but I still need to get the T pulse into rpms. I will try the interval with interrupt to see how it works..

            Thanks again

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            • #7
              Can you improve/change the sensor so that the pulses are more regular? What kind of sensor is it? I have seen misadjusted proxes not pick up pulses evenly from a sprocket or toothed wheel.
              ADEN ENGINEERING
              Automation & Electronic Controls

              Design, Build, Repair, Training

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              • #8
                I tried with interval config and interrupts but the speed rate still going up and down. I tried again with a timer set to 4 and a reset. I got a steady pulse now with CT1 but I don't know how to convert it to RPM. Anyone knows ?
                Last edited by mneira; 02-28-2020, 11:12 AM.

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                • #9
                  Originally posted by johnaden View Post
                  Can you improve/change the sensor so that the pulses are more regular? What kind of sensor is it? I have seen misadjusted proxes not pick up pulses evenly from a sprocket or toothed wheel.
                  Is a pulse generated from a locked Siemens PLC, there is nothing I can do about that pulse.

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                  • #10
                    screen.pdf

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                    • #11
                      To get a time base between CT1 pulses, maybe this timer value store line would work.
                      It will store the time between each pulse and reset the timer value to zero.
                      This stored value could be converted to an engineering unit like RPM.
                      C1 in the picture should be from CT1.

                      Click image for larger version  Name:	Timer Val Store.jpg Views:	0 Size:	42.5 KB ID:	128892

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                      • #12
                        Hey Roger I tried that one and while it gives me a steady rpm, when there is a speed change either up or down the numbers go backwards and it wont go to 0 unles I make a rung to compare it to 0. it is not accurate yet.

                        Thanks for the help. I will keep trying other things

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                        • #13
                          Yep confirmed, if the machine speed goes up the rate speed on the program actually goes down and vice versa

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                          • #14
                            As RogerR mentioned the code is determining TIME not SPEED. You will have to divide a constant number of milliseconds (e.g. 60000 for one minute to get RPM) by the time to get a speed.
                            Last edited by bcarlton; 02-28-2020, 02:33 PM.
                            thePLCguy

                            Bernie

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                            • #15
                              Hello bcarlton,

                              if you look at the Timer Roger posted, the fastest the pulse on C1 the smaller the number in TD1 (Time like you say) will be. If I could reverse that process it will be done. That is why when the machine speed up my speed lowers down. I already have the RPM calculations done.

                              Thanks

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